I believe Ryan is looking to add more options to the panel soon. However you should be able to manual edit this feature within the FTP client currently.
To edit/upload/save/delete files via FTP, you will need to connect to your server via an FTP program. To do so, please follow the below instructions:
Stop your server from the panel.
Log in to FTP using WinSCP (a free FTP software) using the connection details found in the "FTP Details" section of the game server control panel.
Download link for WinSCP here http://winscp.net/eng/download.php
Navigate to the directory or file that you want to edit/delete/upload/change.
After you have finished, save your changes and restart your server from the control panel. You do not need to close out the FTP connection to do so, but you will need to close out any open files.
If you have an issues or need further assistance, please check our wiki at FTP Access.
I have several installed on the server and they are working for me, but no one else can use them unless they also have the .paks installed in their local files too.